1. Technical Field
The technical field relates to vehicle starter systems and more particularly to a vehicle starter system allowing use of the vehicle engine for regenerative braking and supporting operation of vehicle accessories when the vehicle's thermal or internal combustion engine is off.
2. Description of the Problem
Medium duty trucks employed for daytime small package deliveries are subject to relatively frequent stops and extended total idle time due to the urban traffic environment they are often used in and the many stops made for pick-ups and deliveries. Having drivers shut down the internal combustion engine of their vehicle when the vehicle is stopped to avoid engine idling is recognized by firms engaged in this business as effective in reducing fuel consumption and air pollution. However, increasing the frequency of shut downs also increases the frequency of engine restarts and this, in turn, increases wear on the vehicles' starter systems. Package delivery companies have found it economically viable to equip their vehicles with heavy duty starter systems built for durability to handle frequent restarts, notwithstanding the added expense of such systems.
However, even heavy duty electric starter motors accelerate relatively slowly under a cranking load. In addition, due to the step down gear ratios used with such motors, they usually crank the engine at lower RPMs than the engine idles at. Even with the use of a high capacity electric starter motor there can be a delay of a two or three seconds before an engine restarts during cranking. Thus it has been impractical to turn the engine off for many traffic stops due to the delay in following traffic.
Shutting off the engine also cuts power from vehicle accessories which are conventionally mechanically coupled to the engine for power, for example: power steering pumps; and air conditioning system compressors. In addition, some of these accessories are automatically shed when cranking using a starter motor. Engine shut downs done for traffic stops are not seamless operation for the driver due to loss of cab cooling and power steering.